Step-exposing machine for photosensitive materials



Feb- 25, 1941. P. A. FRlEDl-:LL v 2,233,255

STEP-EXPOSING MACHINE FOR PHOTOSENSITIVE MATERIALS Filed sept. 11, 1939 5 sheeis-sheet 1 IFeb. 25, 1941.

P. A, FRIEDELL STEP-EXPOSING HACHINE FOR PHOTOSENSITIVE NATRIALS 5 Sheets-Sheet 2 Filed Sept. 11, 1939 Feb. 25, 1941. P. A. 'FRiEDl-:LL 2,233,255

STEP-EXPOSING MACHINE FOR PHOTQSENSITIVE MATERIALS l Filed Sept. 11, 1959 5 Sheets-Sheet 3 Feb. 25, 1941. P. A. FRIEDELL STEP-EXPOSING MACHINE lhOR PHOTOSENSITIVE MATERIALS 5 sheets-sheet 4 Filed Sept. 1l, 1939 F. A. FRREDELL STEP-EXPOSING MACHINE FOR PHOTOSENSITIVE MATERIALS Filed Sept. 1l, 1.939 5 Sheezs-Shees 5 Patented Feb. 25, 1941 uNrraDl STATES PATENT OFFICE s'rEP-Exrosmd MAonim: Fon. rno'ro- SENSITIVE MATERIALS This invention, a step-exposing'machine for -photo-sensitive materials and method of meas urlng is adapted to the production of step wedges and to the determination of the characteristics and effects of photographic materials and pho` to-sensitive elements including the determination of the photo-actinic power of various sources of illumination as differentiated from the total illuminating power; development of characteristic curve paths; determination of tonal range, exposure factor, speed and sensitivity of photosensitive materials such as plates, films and papers; effects of changes in time ortemperature of development, concentration of developer, elimination, substitution or addition of chemical constituents; production of photographic wedges and scales; and for carrying out various ones of the steps and procedures disclosed in my co-pending application Serial Number 227,365, filed August 29, 1938, for Photographic scale and system of determination and measurement of characteristics of photographic elements.

In the usual processes, taking for instance the test for sensitivity or speed of ja photographic plate, the plate is exposed in a' series of steps by a single revolution' of a sector wheel. With this type of apparatus, adjustments are limited to the speed of rotation and to thestrength oi' the light. This type of machine is cumbersome, requires a great deal of floor space, and is limited as to the number of steps bythe'inertia of the sector wheel, the usual sector wheel exposing about thirteen steps with a factor or ratio of about 1.40. The densities of the respective steps are determined usually by means of a densitometer. Thus the `successive steps receivev exposures equal to about 140% of the immediately preceding steps, and the densities are determined in values of all-light transmitting power instead of in terms of photo-actinic light only. This ratio of 1.40, instead of producing only one step, is capable of producing within its limits at lea-st thirty perceptible steps by my system, for extremely fine measurements, and at least eight steps for normal or ordinarily and very clearly perceptible measurements.

This new machine is 'practically unlimited as to the number of steps and as to the cumulative exposure, and is adapted equally for exposing and testing' lrns, plates, chloride, chloro-bromide and bromide papers, and other photo-sensitive materials. and is universally adjustable as to the exposures of the various steps, and is therefore peculiarly adapted to the production of photographic Wedges and scales.

i The objects of the invention are as follows:

First;

ous-steps. r

Second; to provide a machine as outlined which operates with maximum precision and which is entirely free of cumulative error.

Third; to provide a machine in which the number of steps operating is variable at will for any desired cumulative exposure within the limits of the operating time of the machine.

Fourth;`to provide a machine in which the cumulative exposure is variable at will for any desired number of steps within the capacity of to provide a. machine for exposing Aphoto-sensitive elements in a series of steps with any desired ratios of exposures between the vari- Seventh; to provide a machine as outlined with threshold step and speed indicators to indicate directly the limits of perceptible effects of ex posures on a medium following development of the medium.

Eighth; to provide a. machine which is' quickly and easily unloaded, loaded and reset, even in total darkness. and which after starting, is automaticaily actuated and controlled to expose the successive steps, and to stop the machine and terminate the illumination at the completion of a cycle of operations.

Ninth; to provide a machine of small size, easily handled and conveniently portable, of light weight, simple in construction, and economical the Waterhouse type diaphragm and the method of mounting the diaphragm.

Fig. 6 is a diagrammatic view illustrating the eifect of the threshold speed and range indicator.

Fig. 7 is a side elevation of Figs. 1 and 3, with the ratchet and sprocket housing removed.

Fig. 8 illustrates the method voi mounting an open lamp as a substitute for the enclosed lamp of Figs. 3 and 7.

Fig. 9 is a section taken on line 8 8 of Fig. 3.

Fig. 10 is a rear elevation of the trigger mechanism and automatic control for the timing switch.

Fig. 1l is a wiring diagram for the machine.

Fig. 12 is an enlarged detail view of the shutter feeding mechanism.

Fig. 13 is a full size partial development of the shutter control or timing drum.

Fig. 14 is a graph illustrating the method of determining the setting of the pins on the timing drum for producing a straight log-curve wedge.

or true geometrically-progressive seriesof densities or tones.

Fig. 15 is a fragmentary view showing adaptation of the machine to direct characteristic curve production.

Fig. 16 is a fragmentary view showing the method of constructing and mounting replaceable timing drums. Fig. 17 is a wiring diagram for the adaptation illustrated in Fig. 15.

The machine includes a base 2U or other suitable support and having a plane top 2| forming a bed or support for the material to be tested and for supporting the superstructural parts which include the end bearings 22 and 23 in which are rotatably mounted a timing drum 24 and a feed screw 2l parallel thereto. A guide bar 26 and a shutter slide bar 2`l are non-rotatably secured in these bearings.

A holddown frame 23 is mounted on the bed 2| and securable in some suitable manner, for example by means of hinges 29 and spring clasps or latches 30.

A standard 3|, preferably non-circular in cross section has its lower end cylindricallyformed to snugly ilt in the bore 32 and has a pin 33 which fits in the groove 34 to insure centering of the lamp 3l directly over the holddown frame 28 for equal and uniform distribution of light on the photo-sensitive material I6 during exposure.

The lamp 35 is enclosed in a lamp housing 31 which may be of any conventional form suitably ventilated but must form a perfect light trap. This housing is provided with a diaphragm preferably of the Waterhouse type illustrated and which consists of a disc 38 which is pivoted at 38 and guided and supported in contact with the bottom of the housing by means -of the guard 4l. This disc has a series of precision light pas-A sages 4|, 42, 43, of gradually increasing diameters. the largest of which is equal to the diameter of the passage 44 formed through the bot--` tom of the housing. A sliding diaphragm, not shown, can be substituted. f

It is important that the lamp housing be so constructed that the lamp 33 can be adjusted to bring the envelope of the lamp practically in contact with the diaphragm 38 as illustrated, so that a perfect spread of light rays can be obtained on the sensitive material irrespective of the size of the stop such as 4|, and for this purpose the lamp base support 45 is adjustable as by sliding or telescoping as indicated by the dependent wings 4B. Furthermore, the lamp must center over the stop as shown. An iris diaphragm not shown but well known. can be substituted though there is little likelihood that it would prove completely successful since any slight variation in adjustment would create a very material diiference in the amount of light passed.

This lamp housing is supported by a bracket 41 which has a friction sleeve 43 frlctionally slidable on the standard 3l, and which sleeve is frictionally adjustable through the medium of the screws 4B. The standard 3| is graduated as indicated at 50 in values of relative light strengths on the sensitive material supported on the bed or support 2|.

Thus the light is adjustable as todistance by sliding the bracket 41 on the standard, and also by limiting the quantity of light rays passing to the sensitive material by adjustment of `the diaphragm 3B. The stops 4|, 42, 43 are identied and designated in terms of the relative quantity of light rays passing, so that if a 515 hole is given a value of 1, a inch hole will have a value of 4.

The lamp cord 5| plugs into the machine as indlcated at 52, thus permitting removal of the lamp and substitution of other lamps, as for instance the open lamp illustrated in Fig. 8. It also permits removal of the standard 3| when the machine is not in use.

This standard may be made telescopic as indicated by the broken sleeve at 53 extending downward from the friction sleeve 4B, but with which construction it would be necessary to transfer the friction creating element from the bracket to the bottom of the sleeve.

The shutter control consists of the timing drum 24 which is provided with a supply of trigger pins 54 equal to the number of step exposures which the machine is designed to produce, plus one, and these pins are preferably formed with a spherical head 55 with cylindrical body 56 of equal diameter and with a reduced diameter penetrating or pin portion 5T, the pin thereby forming its own gauge.

These pins can be set into a metal cylinder in which close fitting holes are provided to frlctiom ally secure the pins. However, a more economical and more satisfactory construction consists in forming the drum out of wood or other suitable similar material; white pine proving very satisfactory, since the pins are easily driven in place and easily removed, thus providing universal adjustment of the timing means.

This drum is calibrated longitudinally in seconds as indicated at 88, and circumferentially in decimal parts of a second as indicated at 59. A spiral is scribed as indicated at 60, and which may be'in the form of a continuous line, though preferably as a tracer El with the dots or holes spaced to divide each main circumferential division into an equal number of parts. For example, with a two inch diameter drum, the circumferential divisions will be 1% inch apart with twenty divisions, these divisions being indicated at B2, and the dots 8| if made inch apart would represent to@ second exposure each with the drum turning one revolution per second.

This drum is ordinarily non-removably mounted as in Fig. 1, since the same drum can be used for an infinite variety of timing arrangements; however, where a great many tests are to be made, the drum is preferably removably and replaceably mounted :as indicated in Fig. 16, in which a plate 53 having one registering pin 64, forms a pilot and seats in a seat B5 in the drum at the drive end, and a spring-urged pivot 66 cooperates with a mating pivot GT at the other end, and by retraction of the knurled head 8l' the drum is released and can be removed.

'I'he reason for introducing this feature lies in the fact that for certain tests, such as threshold speed, exposure factor, characteristic curve production, and the initial step in producing a photographic wedge, and range determinations.

the same pin setting is used; while further steps in producing a wedge, range elongation, and absolute precision tests down to the limits of perceptibility, will all require different pin settings.

For speed, sensitivity, contrast, range, characteristic curves,l developercharacteristics and related tests,`the trigger pins are set in geometrically progressive relation irrespective oi' -the material to be tested; therefore one drum can have this pin setting as a permanent adjustment. For'the final steps in making photographic wedges and for other tests, the pin settings or adjustment of the timing mechanism will have to be changed for every different type and grade of photo-sensitive material and for every change in developer or development, andy these pins are more easily removed and set in their new positions than would be thev adjustment of pins in a T-slot or on a spiral on which they might be clamped. They can be more accurately sety and will act with far greater precision than would be possible with a ribbon provided with apertures and which ribbon would have to be replaced every time that a new timing arrangement was required, although such a ribbon (not shown) could readily be used to actuate the trigger which cooperates with the pins, particularly due to the minute movement required.

As will be noted, the adjustment of this timing device is universal as to the number of included steps and as to the exposure for each step.v Any step can be given the total cumulative exposure or any portion of it down' to'the merest fraction. It is therefore adaptable as a precision timing device for any type of apparatus and operates perfectly for precision photo-printing.

'I'he feed screw 25, when operated at the same speed as the drum, has the same pitch as that of the spiral 60 on the drum, but opposite hand, since the screw and drum turn toward each other, being coupled together by the gears 68 and 10 which are respectively fixed on the drum shaft 1| and on the outer end of the feed screw 25.

This -feed screw is rotatably mounted in the bearings formed in the bearing brackets 22 and 23 as indicated, and the screw and drum are driven in synchronism by perfectly-timed driving means such as a synchronous motor 12 driving through a positive drive, such as sprockets 13 and 14 and chain 15. This motor'preferably has an included gear reduction unit for simplifying construction.

The shutter actuating mechanism and controlling mechanism Vincludes a traveling head H carried by the feed screw 25; a shutter arm; and driving means for ,moving the shutter arm and its associated shutter in a series of steps which are controlled as to elapse-time periods by the timing drum.

The traveling head H consists of a frame hav ing a base 16 having an integral hub 11 whichis slldable and rotatable on the rod 26, and a half nut 18 is formed in the underside of the base and rests on and cooperates with the feed screw 25, whereby, when the feed screw is rotated, the head will be carried from one end of the screw to the other, and will permit the head to be tipped up and about the rod 26 to clear the half nut from the thread for manual return of the head to its initial or starting position.

A pair of arms 18 project upwardly from the base and have pivoted therebetween as indicated at 80, a trigger having a depending rigid arm 8| having an integral rigid lever 82v extending oppositely from the pivot as far as the adjusting screw 83 and continuing therefrom in the form of a leaf spring 84, the urgence of which is controlled by means of the adjustable screw 85 which is adjustably secured in the overhanging arm 86 which is supported by the base 16, and a flange 81 continues along the base and forms means for securing the Microswitch 88 in position through the medium of the screws 89; the screw I3 cooperating with the plunger 80 on the switch.

The screw 83 lis adjusted to adjust the trigger 8| for correct cooperation with the trigger pins 54, after which the screw 85 is adjusted until the urgence oi the spring causes the plunger 80 to be depressed to open vthe switch, this being a normally-closed switch. Thus, when a pin 54 engages the trigger, the screw 83 is raised, per-v mitting the switch to close, and as soon as the pin leaves the trigger the spring 84 instantly opens the switch. The actual movement required at the point of the screw 83 to allow the switch to close or to open it is less than onethousandth o f an inch, so that an almost imperceptible movement of the trigger is required and the actual contact with a pin can be extremely brief, and the tension of the spring 84 need be only a few ounces, therefore instant response is attained, and each time a pin touches and lleaves the trigger, a circuit is closed Aand opened through the switch 88.

A passage 8| is formed through the bed 36 of the machine for the circuit cable 82 which is very flexible, and this cable passes to the switch 88 through the eye 83 which is integral with the base 18. y

The shutter arm consists of a sleeve 94 which is slldable on the square 'bar 21 and which sleeve has forwardly-projecting ears 95 between which oneend of the shutter arm proper 86 is pivoted as indicated at 91, so that the shutter arm proper with its shutter 88 can be swung back out of the way for placing the photo-sensitive material 36 in position and for its removal, and this arm has a finger portion 88 for convenient lifting of the arm, and the arm rides on top of the holddown frameas shown.

This arm has an inclined lip |00 which almost touches the sensitive material 36, the inclination preventing reflections onto the material, and also provides a sharp deilning margin to the steps, and this arm also has a projecting shelf |0| t'o which one end of the shutter or blind 88 is attached.

The shutter 98 is formed of very light weight opaque material and is preferably formed as indicated with the main shutter portion flat and having the sides |02 and |03 formed up at right angles and terminating in horizontal flanges |04 and |05 which rest on the guide bars of the frame to form a perfect light seal for the material under test, and yet to be free to permit the shutter to be swung up out of the way for loading and unloading of the material.

'I'he holddown is constructed in the form of a rectangular frame' 28 having a plane bottom surface and a shutter guide bar |08 along each side on top. and the walls |02 and |03 of this shutter fit between these guides and the flanges |04 and@ |05 rest on top of them.

This frame is provided with removable threshold indicators |01 which extend throughout the length of the .frame and are located with their undersurfaces in contact with the material clamped by the frame. A very satisfactory material for making these indicators is strong black thread drawn taut.

This machine is adapted for testing strips, ribbons or sheets of sensitive material, and also for spooled material such as roll films, for which a roll housing |04 is provide at each end of the bed 2|. Each roll housing is provided with a telescoping cover |09, and one of these covers is provided with a key I i for winding the film Il from one spool to the other spool H2, thus the remainder of the film is fully protected while a portion thereof if being exposed.

The driving or transporting means'for the shutter consists of a flexible band, such las a belt or chain H3 which operates over a pulley I4 at one end of the machine and over a sprocket H5 at the other end, and the band is intermediately attached to the sleeve 94 as indicated at H8. If this band is made of belting or ribbon, it is provided with holes for the sprocket teeth. The sprocket ||5 is fixed on the shaft ||1 which is supported by a dependent bearing H5, and forms positive cooperating means for the band.

The driving means for the shutter arm consists of a ratchet H9 which is also fixed on the shaft H1; and a driving and control apparatus4 consisting of a slide which is slidabl;v supported on a dependent slide bearing |2| and which has a pawl |22 formed directly from the upper wall which is formed of spring material, and this spring pawl has a release lever |23 fixed thereto and projecting out through the side wall of the base 20 of the machine, and the outer end of the slide bar |20 is turned up as indicated at |24 to form a combined gauge and stop for gauging the travel of the shutter for each step as indicated at |25. This gauge engages the next following tooth |25 as the shutter is advanced to stop movement of the shutter and exactly space the steps, thus entirely eliminating the necessity for stop pawls or brakes and the consequent friction introduced. This slide bar and its associated elements are made as light in weight as possible, as is also the shutter arm and its associated elements, thus reducing inertia to a minimum and reducing the power required for operation and assuring precision timing and instantaneous action and response. The total weight ci' all of these parts does not exceed a few ounces.

Attached to the inner end of the slide bar |2|l is the core |21 of a solenoid |25, and suitable springs |28 retract the core and reset the pawl |22 and release the stop |25, and a screw |30 forms an adjustable stop for precise limited movement of the slide for retraction to just sufilcient degree to permit the pawl to engage the next tooth.

The solenoid |25 has a stop screw |3| which is adjustable to limit the movement of the core, and its correct adjustment is such that the gauge |25 stops the ratchet -by engagement with a tooth as indicated at |25 at the same instant that the core |21 engages the inner end of the screw Ill, thus preventing any possibility of wedging or springing of the gauge |25.

The terminal step timer and machine control consist of a normally off" Microswitch" |32 which is mounted on top of the bearing bracket 23 upon which an anchor block |33 is formed and upon which block a leaf spring |34 is mounted and which normally depresses the plunger |35 to close the switch, and the correct tension is provided in this spring by the tension adjusting screw |31. A boss |35 is formed on the traveling head H and is threaded to frictionally secure an adjustable stop |35. This stop cooperates with the free end of the spring |34 and forces it away from the switch plunger |35 at the instant that the timing drum reaches its zero position; permitting the switch to break the various circuits including that to the lamp 35. A manually controlled switch is wired in series with the switch |32 for manual starting of the machine.

Fig. 11 is a Wiring diagram for thismachine. The source of potential is indicated by wires |4| and |42, and the wire |4|, switch |40 and switch |32 are connected in series, while the motor 12 is connected through wires |43 and |44 respectively to the switch |32 and .line |42. The lamp 35 is connected in parallel with the motor through wires |45 and |48, and the solenoid |25 is also connected in parallel with the switch Il in series, through wire |41, solenoid |25, switch 88 and wire |48 to line |42.

The adjustment of the machine is carried out as follows: The spiral indicator is centered with `the trigger 8|. A trigger pin 54 is located at the zero position |49 on the timing drum. The head H is moved to the terminal end of the screw and the drum is turned until the pin |49 just touches the trigger. The screw or stop |35 is then adjusted to just contact the spring |34. The drum is then rocked forward slightly and the blick of the two Microswitches noted, and the screw is adjusted until the click of the two switches is simultaneous. Thus the machine will be stopped and the light turned off at the exact zero position. The pin at the zero position is now removed.

For tests of speed, sensitivity, exposure factor, range, for production of characteristic curves, and for initial steps in making a photographic wedge, the respective exposures are calculated according to the formula n-l L R- in which for geometrically progressive series, and the pins are set in the drum counting from zero according to the respective values, but placing no pin at zero.

Fig. 13 shows gcometrically progressive pin settings for the low exposure end of the drum and based on R=1.019. The first pin setting |50 is on .50 second=F in the above formula, and the second pin setting |5| is on .54 second.

If ordinary round headed pins are used it will be necessary to use a gauge for height, a suitable type being indicated at |52 in Fig. l, to insure micrometric precision, since any variation in projection of the pins will affect the accuracy of timing. The shouldered pins are preferable.

'trigger pin as |54. the height of the lamp 35 and the diaphragm' or pins set in friction holes with suitable stops and with the pins of exactly equal length.

Taking the testing of roll nlm, the shutter and shutter arm are swung up jout of the way. the latches 30 are released and the holddown frame is lifted. The roll film is placed in the left hand spool housing, threaded along the bed as indicated at 36 and started on an empty spool ||2 and inserted in the other housing; the covers |08 are applied and the film is wound by means of the thumb blades until the first end oi' the illm reaches the inner'end |53 of the film housing extension. The holddown is then dropped in position and latched, and the shutter dropped in position on the holddown. The shutter arm is located at the left hand end of the slide rod and the traveling head H is located just to the left of the first cooperative Switch |40 is open and have been adjusted.

Switch |40 is now manually closed closing the motor circuit and the lamp circuit. starting rotation of the drum and travel of the head H. As the drum rotates, the first pin |54 wipes the trigger 0| and lifts the screw 83 `permitting switch 80 to close the circuit to solenoid |28 which draws the core |21 against the action of springs |29 and draws the pawl |22 which engages a ratchet tooth, rotating the ratchet which through its shaft and sprocket pulls the shutter arm to the right until the movement of the core is stopped by the screw |3l. Coincidently the gauge |25 has moved under the next following tooth as indicated in Fig. 12 and stopped the ratchet and the shutter. As the trigger pin leaves the trigger, the spring 04 depresses the plunger 90 on switch 8B breaking the circuit to the solenoid and the springs |29 instantly retract the core |21 and cause the pawl |22 to take up another tooth ready for the next shutter operation, the retractive movement of the core be,- ing stopped by the stop screw |30.

This movement is repeated each time a trig ger pin wipes the trigger until the last one |50 has been passed, (Fig. 13). the head H continues to travel until the stop |39 contacts the springy |34, permitting switch |32 to open and breaking the circuits and stopping the machine and extinguishing the lamp:

The switch |40 is now manually opened. the shutter arm with its shutter, and the holddown are raised, and the exposed material advanced or removed, after which the head H is tipped to clear its feed screw and the pins and moved back to its starting position; the release |23 is lifted to cause the pawl to clear the ratchet teeth, and the shutter is moved back to its starting position. The machine is now ready for` another operation;

The exposed material is developed in a master developer and the nega-tive produced or the print produced in the case of positive material will have an unexposed strip for each indicator |01, and at the low exposure end, the step in which this strip is finally visible is the' threshold step and the exposure given this step is the threshold exposure factor of the material when multiplied by the power of the lamp on the material during exposure.

In fitting up this machine, the illuminating power of one lamp only and for only one distance, is determined by known means, establishing a master source of illumination. and further determinations are made photographically by given theinitial black step. which multiplied by the power of the lamp on the surface of the material, and by the ratio of the squares of thedistanceof the lamp in inches and of 12. establishes the exposure factor of the material in foot-candle-seconds.

To determine the relative power of any other lamp thereafter and for determining the ratios between the stops of the diaphragm, the process is repeated, substituting the lamp or stop for making the exposures, and the exposure given the initial black step divided by the exposure of the initial black step in the previously mentioned master print establishes the relative speed. Thus the relative true photo-actinic value of any source of illumination can be accurately determined. Photo-electric meters and similar devices cannot be used for other than the initial or master determination since such devices are sensitive to all light, both photo-actinic and non-actinic, and therefore provide no true measure of photo-actinic values.

blind.

Fig. 6 may be considered either as a print made from the speed test negative or as a direct test of the speed of a paper. If it is a print from the negative, the unexposed indicatorline will appear as a black line extending throughout the series of steps until it reaches the initial black step where it will be blocked out as in |55, and will be barely visible in the next higher step and the exposure given this step establishes the relative speed of the negative material. These tests can be carried out on materials which develop in color and the tests are therefore not limited to black and white.

If Fig. 6 is considered as a positive material test, such as bromide, bromo-chloride or chloride paper exposed directly in the machine, then the indicators |01 will appear as a white line |51 and this line will fade out completely in the initial white step |58 and be just barely Visible in the next higher exposed step |59, thus establishing by the exposure given step |59 the threshold speed of the paper, while the exposure factor of the paper is determined by the exposure given the initial black section |55.

DevelopersV are tested by the same process but substituting the developer under test for the master developer.` The variations or shifts in tones, tonal range,'threshold speed and exposure factor as compared with the master print establish the relative values of speed and contrast characteristics of the developer under test.

For making photographic wedges either positivev or negative the initial process is carried out as previously outlined for speed tests and the threshold step determined. A second strip of the material is then exposedwith the lamp adjusted to bring the entire range of the material within the limits of the series of steps.

Taking negative material as an example. Suppose that the indicator line fades out in step 3| Thus this Step its is the threshold step.

In other words they are color- (see Fig. 13), at |88, the exposure of which is 5.4 seconds. The lamp or the diaphragm must then be adjusted to give 5.4+.5 (the ilnal step exposure)=10.8 times the illumination on the surface of the material. which will bring the fade-out of the indicator down to step I. The method is more explicitly presented in Fig. 14

lfrom this point.

In Fig. 14, the line a is the actual exposure curve ot one material tested, and starting with an exposure of 1.2 seconds exposure for step 2. and terminating with 95 seconds for step 60 at |82. b is the actual curve of densities determined and measured photographically. c is the coordinated exposure density curve in which the overall density is elongated to the same value as the total exposure, and d is the new exposure curve which is plotted as follows: Take step |8 at |88. A vertical |84 is carried to intersect the exposure curve a at |85 and then carried horizontally from this point to meet the coordinated curve c at |88, then carried vertically to the exposure curve a at |81 and then horizontally to an intersection with step line I8 at |88. Thus, while step I8 was originally given an exposure ot 3.98 seconds, the exposure for this step must be increased to 10.55 seconds to bring it directly on the exposure curve a, which will be converted into the density curve. After all transfers are made as indicated by the dotted lines, the new exposure curve d is established and the drum on the machine is reset or adjusted to these new exposures, and a negative or positive made from the same material with this new series of exposure will produce a series of densities or tones which will fall directly on the straight log curve a and therefore will form a perfect wedge.

In Fig. 15 is shown a modification of the invention which directly develops the characteristic curve path of the material. This involves no other changes than the addition of another shutter with its supporting and driving means and a modied holddown, with the two shutters operating at right angles to each other and selectively, and includes all of the previously described elements and mechanisms including the bed 2|, which however must have sufficient area to form a square support for the material to be tested.

The modified frame is square as illustrated, and if of any appreciable size, aligning means will be required for the shutter and which is illustrated as consisting of racks |88 for cooperation with the pinions |18 and |1| which are fixed on the respective ends of the shafts |12 which are rotatably mounted in the shutter arms as indicated at |18, all of these shutter mechanisms being made as light in weight as possible. The pinions and shafts can be made of fiber, Bake1ite, or magnesium-aluminum alloy.

The wiring diagram is illustrated in Fig. 17. 'I'he right hand of this diagram is a duplicate of Fig. 11 with the modification of the two-way switch |14. The extension involved in this diagram consists of a second solenoid |15 which is selectively connectable in circuit.

When this switch is closed to contact |18, the circuit is completed by trigger pins 84 actuating switch 88, to close through wire |41, solenoid |28, contact |18, switch arm |14,'wire |11, switch 88, wire |48 to line |42; while when the switch is closed to contact |18, the circuit is broken for the solenoid |28, and completed through wire |19, solenoid |15, wire |88, contact |18, switch arm |14, wire |11, switch 88. wire |48 to line |42.

The operation is as follows: A sheet of material |8| to be tested is clamped by the frame |82. Shutter arm |88 has its step-defining edge or lip |84 moved to the inner edge |88 of the frame, and shutter arm |88 is moved completely oil.' of the frame as shown.

Switch |14 is moved to contact |18, after which switch |48 is closed, starting the timing mechanism and the lamp, and the shutter |81 exposes the sheet in a series oi steps |88, and as the head H with its stop reaches the switch |82 it breaks the circuits to the motor and lamp, completing exposure of the ilnal step and stopping the machine.

Switch |48 is now manually opened; the head H is moved back to its starting position; the arm |88 is moved to the outside of the frame |82 at the right, and shutter arm |88 is moved to the head end of the frame with its step-denning edge or lip |88 in contact with the inside edge 18| o! the holddown frame.

Switch |14 is closed to contact |18 after which switch |48 is closed. The exposures are thus duplicated at right angles to the rst series as indicated by the steps |82, and after `the shutter |88 has completed its exposures the machine is again automatically stopped, switch |48 is manually opened, and the material |8| is removed and developed.

The result is fragmentarily illustrated in one corner of the holddown frame by means of relative density values. It will be noted that duplicate exposures occur at diagonally opposite corners, the exposures being equal to the sums of the step exposures indicated at |84 and |95, the values being taken at |88 as relative -densities for purposes o! explanation instead of the sum ci the two exposures.

The densities will not follow the relative exposures due to their being affected by the characteristic curve oi the material. The duplicate exposures at the two diagonally opposite corners are taken as a base, and the square in each step which has the same density as the diagonally related base squares, as |81 and |98, are determined, and a curve |88 is drawn through the centers of these squares, forming the characteristic curve of the material. The densities are determined as previously outlined or by means of a densitometer, since the actual photo-actinic values are not important where the characteristic curve is to be plotted.

The holddown frame, Fig. l, is provided with graduations 288 so that the machine may be used for whatever number of steps is desired, or to conform to the length of the material to be tested. When the full scale is not used, the head H is set for cooperation first with the trigger pin which is identified with the starting step.

The steps need not be greater than one-eighth inch each, therefore one hundred steps can easily be formed on a twelve inch strip oi' sensitive material.

In testing materials, all Contact papers can be tested for speed with the same setting and lamp adjustment, and likewise al1 bromide and bromochloride papers can be tested with the same settings, requiring only a different lamp adjustment than the chloride papers, and the same applies to al1 ultra-sensitive materials, such as films and plates.

For this reason, narrow strips can be cut from a number of different materials of the same class, backbound with scotch tape to form a mat and exposed simultaneously and developed. With an inside width of three inches in the holddown, and

material cutin one-quarter inch ribbons, twelve 'different grades or makes oi materials can be tested simultaneously. An indicator |01 is provided for each ribbon of material.

Obviously, a iilm or ribbon could be used for` could be readily operated by the trigger Il by having the escapement bar with which the type bars cooperate in a typewriter. cooperate with this trigger, but a ,greater movement of the trigger would be required. reducing the responsiveness and sensitivity of the machine, therefore the structure illustrated is obviously the most emcient and rapidly responsive and .operates with utmost precision and is therefore the preferred form of the invention.

It will be understood that variations in construction and arrangement Vof parts, and variations in the process, which variations are consistent with the appended claims, may be resorted to without detracting from the spirit or scope of the, invention, or sacrificing any o! the advantages thereof.

I claim:

l. A photo-sensitive material exposing and measuring machine, in combination, means for supporting a photo-sensitive material; a shutter and step driving means for driving said shutter in a series of steps throughout the length of the material; a lamp for exposing said material as said shutter permits access of light from the lamp thereto; timing means controlling said shutter and initiating movement thereof for each step, and means included in said timing means and comprising a timing element foreach step, said timing elements being individually and manually adjustable for selective adjustment to establish any desired elapse time periods between any two successive shutter movements without affecting the timing of other shutter movements; driving means for said timing means, and means manually operable for starting operation of said machine and coincidently lighting said lamp, and

operation terminating means included in said timing means extinguishing said lamp and terminating operation of said driving means after said shutter has been moved to the end of its series of steps and coincident with termination of the elapse-time period for the last step.

2. In combination, a support and holding means for photo-sensitive material; a shutter for protecting said material and movablev to expose said material in a series of steps; shutter driving means associated with said shutter for moving said shutter instantaneouslyl through the length of each step; control means for said shutter-driving means for initiating actuation thereof, said control means including a timing element for each step for establishing the elapse-time periods between successive actuations of said shutter-driving means and the resultant movements of said shutter, said timing elements being selectively manually adjustable for independently and selectively establishing the elapse-time periods between any two successive steps without affecting the elapse-time periods of other steps; synchronous driving means for said control means and the included timing means; a source of illumination; means manually operable for starting said synchronous driving means and coincidently creating illumination of `said source oi illumination; and means included in said timing means terminating operation of allot said means.

3. A photo-sensitive material measuring ma.

chine, in combination; means for supporting a photo-sensitive material; a shutter and step driving means for driving said shutter in a series of steps throughout the extent of the material;

a lamp for exposing said material as said shutter permits access of light from the lamp thereto; timing means controlling said shutter and initiating movement thereof for each step; and means included iny said timing means and manually adjustable to establish any desired elapse time periods between successive shutter movements; driving means for said timing means, and means manually operable for starting operation of said f machine and coincidently lighting said lamp. and

operation terminating means included in said timing means lextinguishing said lamp and terminating operation of said driving means after lns said shutter has been moved to the end of its series of steps and coincident with termination of the eiapse-tlme period for the last step; a second shutter operable at right angles to said shutter and a second step driving means for said second shutter; and means associated with said timing means for transferring control from. said shutter to said second shutter to carry said second shutter through a series oi duplicate steps at right angles to the ilrst series produced by said shutter first mentioned.

4. A photographic exposing and measuring machine comprising a support; sensitive material holding means associable with said support; a drum and a feed screw operating in' parallel and synchronous driving means therefor; trigger pins located on said drum; a traveling head carried by said screw; a normally-closed/switch carried by said head and a trigger carried'by said head in cooperative relation to said trigger pins and including a tlrst switch-control member urging said normally-closed switch to open; cooperation vof any one oi' said pins with said trigger overcoming the urgence of said first switch-control member to permit said switch to close; a-source of illumination; a second switch-control member mounted on said head and a second switch mounted in cooperative relation to said second switch-control member and separate from said head; said second switch-control member acting to open said second switch when said head reaches its terminal of travel to extinguish said source of illumination and stop said synchronous driving means; a shutter' unit operating cooperatively with said holding means and including an arm and a support for rectilinear travel thereof; a continuous flexible band attached at one point to said arm and operating over rotatable members one of which cooperates positively therewith and a ratchet ilxedly associated with said one; a slide element including a pawl and a gauge for cooperation with said ratchet; a solenoid having a core connected to said slide elelment and retracting springs associated therewith; said rst switch controlling operation of said solenoid to move said shutter in steps in accordance with the relative positions of said pins means cooperatively related to said holder for exposing said material in a series of steps; timing means including a manually adjustable timing element for each step for controlling time-elapse periods between successive step movements of said shutter; said timing elements being indivldually and selectively adjustable for changing the time relation between any two steps at will without affecting the time relation between. other steps; instantaneously-acting driving means controlled by said timing means and including movement limiting and gauging means for said shutter; means manually controlled for initiating operation of said machine and coincidently illuminating said source of illumination; and means included in and controlled by said timing means and associated with said machine terminating operation of said machine and of said source of illumination at the completion o! the elapse-time period following the terminal movement oi' said shutter.

6. A photographic exposing and measuring machine comprising a holder for photo-sensitive material; a source of illumination; shutter means cooperatively related to said holder for exposing said material in a series of steps; timing means controlling time-elapse periods between successive step movements of said shutter; instantaneously-acting driving means cont trolled by said timing means and including movement limiting and gauging means for said shutter; means manually controlled for initiating operation of said machine and coincidently illumination; and means included in and controlled by said timing means and associated with said machine terminating operation of said machine and of said source of illumination at the completion of the elapse-time period following the terminal movement of said shutter; second shutter means cooperatively related to said holder and operable to expose said material in a series of steps at right angles to said first mentioned series and including second instantaneously-acting driving means controlled by said timing means and including gauging means for said shutter, and manually controlled means for transferring con; trol from one instantaneously-acting driving means to the other, whereby said material, through two operations oi said machine sequentially through the respective shutter means is exposed in two right-angularly-related series of steps of equal exposure values to establish a characteristic curve path for the'material.

1. A structure as defined in claim 5; a threshold-speed registering and indicating device associated with said sensitive material holder and comprising a narrow opaque element extending throughout the length of said holder for forming a continuous unexposed line throughout the entire series 0f steps upon exposure of said photo-sensitive materialufor establishing the threshold step in the material by the step in which the line is no further traceable due to lack of contrast between the unexposed line and the remainder of the area of the step, following development of the material.

8. In combination. exposing means for a photosensitive material, and instantaneous driving means for moving said exposing means sequentially in a series of steps including a last step; means gauging the movement oi said exposing means for equal movements for the respective steps; timing means controlling said driving means and including a timing element for each step with each element selectively manually adinstable for individually establishing the elapsetime period between any two steps without afiecting the time-elapse periods between other steps; synchronous driving means for said timing means; a source of illumination; means manually operable i'or initiating operation oi' said synchronous driving means and of said source oi illumination; and means associated with said timing means terminating operation of said synchronous driving means and of said source of illumination at the instant of the termination of the exposure period for said last step and forming the timing means therefor.

9. A photo-sensitive material exposing machine comprising; a holder for photo-sensitive material and a source of illumination for exposing said material; a shutter and step driving means therefor for exposing an increased area of said material with each movement oi' said shutter; control means for said driving means for timing the shutter movements and comprising a drum, a timing element for each movement oi the shutter, said timing elements being each independently adjustably secured in said drum for manual adjustment of the elapse-time period between any two successive shutter movements without atl'ecting the time-ellipse periods between other movements; means for driving said drum at a constant speed; a traveling control member mounted in cooperative relation for sequential cooperation with said timing elements and actuated sequentially by said timing elements for initiating actuation of said driving means for the successive movements oi" the shutter; transporting means for transporting said traveling control member parallel to said drum; and on operative connection between said drum and said transporting means lor driving said transporting means at a predetermined speed relative to the rotational speed oi said drum.

1i). In a sensitometer having a shutter and step driving means therefor for exposing a strip of photo-sensitive material in a series oi steps by successive movements of the shutter; controlling means for controlling the timc-elapse periods between successive movements of the shutter comprising; an individual timing element for initiating each actuation oi said step driving means; a supportfor all of said timing elements, with each timing element individually manually adjustable on said support for changing the relative timing of any one timing element at will without affecting the timing of the other timing elements; actuating means cooperatively related to and sequentially actuated by said timing elements and operatively associated with said step driving means for actuation thereof coincident with cooperation of a timing element with said actuating means.

11. In a sensitometer having a shutter and step driving means therefor for exposing a strip of photo-sensitive material in a series of steps by successive movements of the shutter; controlling means for controlling the time-elapse periods between successive shutter movements comprising a drum having a thread formed spirally throughout its length and functioning as a timing element locating guide; a timing element for each shutter movement and supported by said drum and projecting from the periphery thereof and located along said thread and individually manually adjustable therealong for. adjusting the time-elapse periods between any two successive shutter movements at will; transporting means operating parallel to the axis oi' said drum; and

actuating means supported and transportable by said transporting means throughout. the length of said drum and in cooperative relation to said timing elements for sequential actuation thereby, and operatively associated with said step driving means for initiating actuation thereof coincident ,with actuation of said actuating means by a timing element; 'and means for driving said drum at a predetermined speed and coincidently driving said transporting means for constant registry of said actuating means with the thread on said drum.

12. In a sensitometer having a shutter and electrically actuated step driving means therefor for exposing a strip of photo-sensitive material in a series of steps by successive movements of the shutter, and a source of exposure illumination and a circuit therefor; controlling means for controlling the elapse-time periods between successive movements of the shutter comprising; a rotatably mounted drum having a pin-locating thread formed spiraliy thereon, and timing elements comprising pins removably secured in said drum and removable and replaceable to any position along said thread for changing the timeelapse periods between any two successive movements of said shutter and including a pin for each shutter movement; a feed screw rotatably mounted parallel to the axis of said drum and extending throughout the length thereof; a switch and a support therefor supported by said screw and transportable thereby along said drum in cooperative relation to said pins for sequential actuation thereby, and an operative connection between said switch and said driving means for initiating actuation of said step driving means coincident with cooperation of said switch with each pin., and driving means for driving said drum and said screw for synchronism between the travel of the switch and that of the thread.

13. A structure as defined in claim 12; an ad- ,instable member carried yby said support and projecting in the direction of travel; a switch fixed- 1y mounted in cooperative relation to said adjustable member and controlling the circuit for said source of exposure illumination and normally maintaining said circuit closed; said adjustable member effecting opening of the last mentioned switch at the instant when said support reaches its terminal of travel following the nal shutter movement and forming the timing element for controlling the exposure of the last step.

PHmIP A. 

